As to the conventional methods of forming a ceramic layer on the metallic or the cermet body, there are known CVD and PVD vapor deposition methods and plasma spray coating method, etc.
Further, a method for sintering a ceramic powder, a metal powder, or a mixture thereof, which utilizes the heat developed by Thermit reaction as the heat source, is disclosed in Japanese Laid-Open Patent Application No. SHO 61-186404 (which corresponds to U.S. Pat. No. 4,761,262). However, as far as the knowledge of the applicant of the present invention is concerned, no techniques have heretofore been developed, which provide the method of forming a sintered ceramic layer tightly bonded to a metallic or a cermet base material.
The above-mentioned CVD and PVD vapor deposition methods, etc. quoted as prior arts have so far involved problems or points at issue, in particular, on the bonding of coating on metals and cermets, and are unable to provide excellent characteristics of ceramic layers themselves such as resistance to abrasion, resistance to oxidation, and resistance to corrosion, etc.